The objective of this Phase II project to is to validate a companion diagnostic to predict response to targeted anti-angiogenic therapy (i.e. VEGFR inhibitors) in patients with late stage kidney cancer. Several such treatments have been FDA approved but only a minority of the patients benefit from this therapy. Oncologists who treat kidney cancer declare a strong need for tests to help them predict which patients will respond to VEGF inhibitors so that likely non-responders can be given alternative treatments. To date, there are no companion diagnostics for kidney cancer as there are for breast, colon, and lung cancers. Our multiplex IHC test uses an aggregate score derived from several proteins in the VEGFR pathway that were identified using our patented platform technology for biomarker identification. Based on testing from 51 RCC tumors, surgically removed from patients before treatment with a leading VEGF inhibitor, our biomarker panel correctly identified classified 27 out of 33 responders and 15 of 18 non-responders. To date, there are no biomarkers with comparable predictive accuracy reported in the literature. The Phase II project will involve rigorous analytical and clinical validation using up to 250 new patient samples.